I rented Seinfeld's video this past weekend (from 198x) (86?) (87?) (one of the two). While his standup routine was definitely very funny, the little skits he did in between to be rather dumb and quite boring. They were kind of like 'bad' Saturday Night Live skits.
Also, some of the jokes he told in the standup part of the video have been used on the show - and in his Saturday Night Live monologue (which was great) - so the jokes seemed kind of old and stale.
But, if you like Seinfeld (we all do, right?), rent it for a laugh.